Use python3 instead of python when calling the mutlib-generator

Upstream-Status: Pending

Signed-off-by: Mark Hatle <mark.hatle@amd.com>

Index: gcc-13.3.0/gcc/config/riscv/multilib-generator
===================================================================
--- gcc-13.3.0.orig/gcc/config/riscv/multilib-generator
+++ gcc-13.3.0/gcc/config/riscv/multilib-generator
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # RISC-V multilib list generator.
 # Copyright (C) 2011-2023 Free Software Foundation, Inc.